Air conditioning apparatus with provision for selective reheating



June 14, 1960 ARMSTRQNG 2,940,281

AIR CONDITIONING APPARATUS WITH PROVISION FOR SELECTIVE REHEATING Filed Nov. 25, 1958 OUTDOOR FIG. 2.

YHPO RH TOR .E'VHPORFITOR COOL FIGS- OUTDOOR FEHEHTER EVHPORHTOR CONDENSER DEHUMIDIFY \NVENTOR ALFRED ARMSTRONG (9%; ATTORNEY United States Patent AB CONDITIONING APPARATUS WITH PRO- VTSION FOR SELECTIVE REHEATING Alfred Armstrong, East Longmeadow, Mass, assiguor to Westinghouse Electric Corporation, East Pittsburgh, Pin, a corporation of Pennsylvania Filed Nov. 25, 1958, Ser. No. 776,334

4 Claims. (Cl. 62-428) This invention relates to air conditioning apparatus and particularly to a compression refrigeration system in such apparatus for selectively cooling or dehumidifying air.

In maintaining comfortable conditions Within a room or enclosure adapted for human occupancy, both the temperature of the air and the moisture content of the air should be controlled. Conditions of high air temperature and high humidity can generally be corrected by simply cooling the air, because the removal of heat from air possessing a high relative humidity generally effects condensation of moisture from the air. There are periods, however, during which the ambient air temperature is near an acceptable level but human discomfort is experienced, nevertheless, because of high humidity. This invention enables air conditioning apparatus to be constructed which is capable of removing moisture-from the air by cooling the air and thereafter reheating the air to provide conditioned air which has been dehumidified without a substantial reduction of its sensible heat.

In accordance with the invention the air conditioning unit is equipped with two heat exchangers over which the air to be conditioned is conveyed. During periods when both cooling and dehumidification are required the refrigerating system functions in a conventional manner with the two indoor heat exchangers functioning as parallel evaporators for cooling air. An outdoor heat exchanger in the refrigerating system dissipates to outdoor air the heat removed by the indoor heat exchangers. When no cooling, or but a small amount of cooling, of the indoor air is required but dehumidification is required, one of the heat exchangers is converted from evaporator operation to reheater operation for the purpose of returning to air that has been cooled and dehumidified by the other indoor heat exchanger part or all of the sensible heat removed from that air before it is returned to the conditioned enclosure. This conversion of the one indoor heat exchanger is accomplished by bypassing the condenser, or outdoor exchanger, of the refrigerating system and directing warm vaporous refrigerant directly from the compressor into the one heat exchanger. Sensible heat from this warm vaporous refrigerant is transferred in the one heat exchanger to the air being conditioned before the refrigerant is returned to the compressor for recirculation.

Provision for making this operational change in the refrigerating system is made by adding to the basic refrigeration system means including a valve for closing a refrigerant flow path from the outdoor heat exchanger to the one indoor heat exchanger and establishing a bypass path from the compressor outlet to that indoor heat exchanger. The means that provides the refrigerant bypass path includes a restrictor device for expanding refrigerant from the pressure in the condensing portion of the refrigerating system to the pressure existing at the suction, or inlet, side of the compressor, so that the outdoor heat exchanger and the other indoor heat exchanger continue to function to respectively dissipate and absorb heat.

2,940,281 Patented June 14, 1960 The several objects, features and advantages of the invention are elucidated in the following detailed description of which the accompanying drawing forms a part and wherein:

Fig. 1 is a simplified illustration of a unit type air conditioner embodying this invention;

Fig. 2 is a schematic circuit diagram of a refrigerating system embodying the invention; and

Fig. 3 is another circuit diagram of the system showing a different condition of operation.

The air conditioning unit illustrated in Fig. 1 includes a casing 11 having a partition 12 therein which devides the unit into an indoor air section 13 and an outdoor air section 14. The unit is adapted to be mounted in a Window or other opening in a Wall 15 with the indoor section 13 thereof in communication with the indoor space to be conditioned and the outdoor section 14 thereof in communication with a region outside the conditioned space. Disposed within the indoor section 13 are first and second heat exchangers 16 and 17 over which air to be conditioned is circulated by air propelling means, such as a motor driven propeller fan 18. The heat exchangers 16 and 17 are preferably arranged adjacent one another in face-to-face relationship. Indoor air enters the unit through an inlet opening 19, is propelled by the fan 18 first over heat exchanger 16, then over heat exchanger 17 and returned to the conditioned enclosure through an out-. let 20. Moisture condensed from the indoor air by heat exchangers 16 and 17 falls into a collection trough 35 and is conveyed outside the conditioned enclosure by a suitable drain (not shown).

Disposed within the outdoor section 14 of the unit is an outdoor heat exchanger 21 adapted to have outdoor air circulated thereover by suitable air propelling means, such as a motor-driven propeller fan 22. 'Also disposed within the outdoor section 14 is a compressor 23 which, together with heat exchangers 16, 17 and 21, is a part of the refrigeration system illustrated in Figs. 2 and 3. The compressor 23 is preferably housed within a sealed casing which also houses a motor (not shown) for driving thecompressor. The compressor 23 is adapted to pump re,- frigerant through the several heat exchangers of the rerfrigerating system and is provided with an outlet 24 and an inlet 25.

The outdoor heat exchanger 21 functions as a con-v denser and is adapted to receive compressed vaporous refrigerant through a hot gas line, or conduit, 26 which is connected to the compressor outlet 24. Heat is extracted from the refrigerant by outdoor air passing over the heat exchanger 21 and the condensed refrigerant is delivered to indoor heat exchanger 16 through a liquid line, or conduit 27, and a restrictor device, such as a small bore restrictor tube 28. Liquid refrigerant is also adapted, to be delivered to indoor heat exchanger 17 through a ranch of liquid line 27 that is connected to a valve 29. The valve 29 has a rotatable plug 30therein which has a passage therethrough. When the plug 30 is in the posi-. tion shown in Fig. 2 its passage provides communication between liquid line 27 and another restrictor device, such as a small bore restrictor tube 31, which communicates.

with indoor heat exchanger 17 The valve 29 also controls the flow of refrigerant through a bypass circuit that connects the outlet of the,

outlet 24 and valve 29. The plug 30 of this valve when rotated to the position shown in Fig. 3 establishes con 1-.

munication between the hot gas line 26 and a bypass lineor conduit 32 which discharges refrigerant through, an-

other restrictor device, such as a small bore restrictor tube 33, into indoor heat exchanger 17. Theo'utlet ends refrigerant vapor.

by means of a suction conduit 34 to the compressor in- It will be noted by comparing Figs. 2 and 3 of the drawing that valve 29 selectively establishes a refrigerant flow circuit from heat exchanger 21 through line'27' and tube 31 to heat exchanger 17 or from the compressor through lines 26 and 32 and tube 33 to heat exchanger 17 and that one flow path is'alway s closed, or disestablished, when the other is open, or established. The Fig. 2 position of valve 29, in which refrigerant flows first through the outdoor heat exchanger 21 and then to indoor heat exchanger 17, will be referred to as the cool position of valve 29 inasmuchas, when the valve is so positioned heat exchanger 17 functions as an evaporator to cool indoor air conveyed thereov er. 'The Fig. ;3 po- 7 sition of valve 29, in which warm vaporousw refrigerant is delivered from the compressor 23 to indoor heat exchanger 17, will be referred to as the dehumidify po- 'sition of'the valve inasmuch as, when the valve is so positioned heat exchanger 17 functions as a heater to add heat to room air conveyed thereover.

7 Operation I 7 When high humidity and temperature conditions are jointly encountered audit is, therefore, desirable to both cool and dehumidify indoor air the valve 29 is placed in its cool position (Fig. 2) and the refrigerationcircuitlfunctions in 'a conventional manner with both indoor heat exchangers 16 and 17 functioning as evaporators. High pressure liquid refrigerant leaving outdoor heat exchanger 21 flows, through two parallel quantity of refrigerant in a vaporous state as restrictor tube 28 delivers in a liquid state, tube 33 must be shorter. Stated differently, the actual restriction through tube 33, by standard measurements, is less than the restriction through tube 28 or tube 31. The efiective restriction (i.e., ability to deliver refrigerant at a particular rate) is approximately the same foraall three restrictor tubesbecause tube 33 delivers vaporous refrigerant, whereas tubes 28'and 31 deliver refrigerant that is almost'entirely in liquid state.

The length of tube 28 is, of course-generally fixed by the requirements of the system when operating to both cool and dehumidify the air. The length of restrictor tube 33, whilealway's less than restrictor tube 28, if increased will reduce the. flow of refrigerant to heat exchanger 17 and if shortened will increase the flow of refrigerant to that heat exchanger. Thus, the amount of reheating accomplished by heat exchanger 17 with respect to the amount of cooling performed by heat exchanger'16 can be preset. t

Heat exchanger 16 has a cooling rate that is considerably greater than the heating rate of heat exchanger 17 because refrigerant is vaporized in heat exchanger 16, whereas onlysensible'heatis availablefrom the gaseous refrigerant in-heat exchanger 17. isa desirable relationship, however, because heat exchanger 16 must have a greater heat transfer capacity in order to remove the I latent heat of condensation from the moisture which is paths, which include restrictor tubes 28 and 31. These restrictor tubes are of substantially the samelen g th and ofier substantially the same resistanceto refrigerant flow so that refrigerant is divided equally '7 between indoor heat exchangers 16 and 17. Refrigerant vaporized in heat exchangers 16 and 17 absorbs heat from indoor air conveyed over these heat exchangers and the vaporousf refrigerant is returned to the compressor through suction conduit 34. y 7

-When the temperature of the indoor air is near the desired value but the air contains an undesirable quantity of moisture, the operation of the refrigeration system can be modified to effect dehumidification of the air with little or no sensible cooling by shifting valve 29 to its dehumidify position '(Fig. 3). This disestablishes the refrigerant flow path from the outdoor heat exchanger 21 to the'indoor heat exchanger 17 and establishes a bypass circuit through which warmvaporous refrigerant is delivered to indoor heat exchanger 17, which commences to function as a heater. V

. Refrigerant is expanded from the pressure at which it leaves the compressor outlet 24 to the pressure existing within heat exchanger 17, which is substantially the same as the compressor suction or intake pressure, through restrictortube 33.

v The delivery" of warm vaporous refrigerant at suction pressurerto indoor heat exchanger 17 makes available for airreheat purposes a quantity of sensible heat from the The amount of usable heat depends upon the difference between the temperature of the refrigerant gas conveyed torheat exchanger 17 and the room air temperature. This heat is added to indoor air that has previously been propelled over indoor heat ex- 7 changer "16, which'continues to function as an evaporator to remove heat and condense moisture from thelaina The division of refrigerant flow between heat ex-i changers 16 and 17 when the refrigeration system is ops crating to dehumidify airtcan be predetermined by careful selection of the relative lengths of the two restrictor tubes 28 and 33. As is Well understood, a given length small bore restrictor tubing isicapable of delivering liquid at a higher rate than it can deliver gas. Therefore, in order lemme W a r-Ya atax antes ans.

condensed from the airpassing thereover. V

The refrigerating system incorporating this invention employs substantially standard components generally employed in simple, low-cost, unit, type air conditioners which are designed solelyifor cooling indoor The mere addition of a simple valve 29 and appropriate refrigerant lines or conduits makes it possible for the system to performthe twodistinct air conditioning functions described above. Simplicity and low costare, therefore, features of the invention.

Reheating systems'for 'unit type air conditioners have been proposed in the past. However, .the system embodying this invention possesses, among other things, the advantage that there is little or no likelihood of liquid refrigerant carrying over, or flooding back, into the compressor when the system is operated for dehumidification purposes only.' This is the result of arranging the refrigerant flow circuit (Fig. 3) in such a manner that the warm refrigerant usedfor reheating purposes and conveyed through indoor heat exchanger 17 is returned directly to the compressor 23 while still ina vaporous state This refrigerant is. not condensed and fed into the other indoor heat exchanger 16 as has been done in certain prior systems, with the result that there isno tendency to flood and overflow that heat exchanger (16 which is functioning as an evaporator for cooling indoor air. While it is desirable, as heretofore described, to arrange indoor heat exchangers 1-6 and 17 in face-to-face relationship and pass all of the air to be conditioned first over the. cooling heat exchanger 16 and then-over the convertible heat exchanger l'l, other air flow patterns may be employed. For example, indoor 'air may be 'divided into two streams, one for each of the heat'exchangers 16' and 17, and the air streams mixed after passingcver the heat exchangers and before being returned to the indoor space, which arrangement would function satisfactorily for both coo gand dehumidify operations." i i f I From the foregoing it be seen that .this invention providesa novel and uniquely'eifective refrigerating system for unit air conditioners-adapted to selectively cool and dehumidify' air for a conditioned enclosure. 5

, While the, invention has been shown in but one form, it will be obvious to those skilled in-the art that it isnot so limited, but is susceptibleof various changes and modifications without departing from the spirit thereof.-

What is claimed is:

1. In air conditioning apparatus including a compression refrigeration system, a compressor, a condenser, an evaporator, a heat exchanger, means for propelling air to be conditioned over said evaporator and over said heat exchanger, conduit means connecting said compressor, condenser and evaporator in series for refrigerant flow therethrough in the order named, means including a valve for selectively routing refrigerant from said condenser through said heat exchanger to said compressor or from said compressor to said heat exchanger and back to said compressor, bypassing said condenser and said evaporator, said last-named means including a first restrictor device for regulating refrigerant flow from said condenser to said heat exchanger and a second restrictor device havins less actual restriction than said first restrictor device for regulating the bypass refrigerant flow from said compressor to said heat exchanger, whereby said heat exchanger can be selectively operated as an air cooling device or an air heating device.

2. in air conditioning apparatus including a compression refrigeration system, a compressor, an outdoor heat xchanger, first and second indoor heat exchangers, conduit means connecting said heat exchangers for directing refrigerant from said compressor through said outdoor heat exchanger, through said indoor heat exchangers in parallel flow relation and back to said compressor, means including a valve for stopping the flow of refrigerant from said outdoor heat exchanger to said second heat exchanger and establishing a refrigerant flow path from said compressor to said second heat exchanger and back to said compressor, bypassing said outdoor heat exchanger and said first heat exchanger, said last-named means including a restrictor device in said refrigerant flow path between said compressor and said second heat exchanger, and

means for conveying air to be conditioned over said first and second heat exchangers.

3. in air conditioning apparatus including a compression refrigeration system, a compressor having an inlet and an outlet, first, second and third heat exchangers each having an inlet and an outlet, conduit means connecting the outlet of said compressor to the inlet of said first heat exchanger, conduit means connecting the outlet of said first heat exchanger to the inlets of said second and third heat exchangers and defining a refrigerant flow path to each of said second and third heat exchangers, a restrictor device in each of said refrigerant flow paths, means including a valve for closing said refrigerant flow path to said third heat exchanger and connecting the outlet of said compressor to the inlet of said third heat exchanger, said last-named means including a third restrictor device, conduit means connecting the outlets of said second and third heat exchangers to the inlet of said compressor, and means for conveying air to be conditioned over said second and third heat exchangers.

4. in air conditioning apparatus including a compression refrigeration system, a compressor, a condenser, an evaporator, a heat exchanger, a discharge line connecting the outlet of said compressor to said condenser, a first refrigerant line including a restrictor device connecting said condenser to said evaporator, a second refrigerant line including a restrictor device connecting said condenser to said heat exchanger, a section line connecting said evaporator and said heat exchanger to said compressor, whereby refrigerant can be circulated from said compressor through said condenser to said evaporator and said heat exchanger, a bypass line having a restrictor device therein connecting the outlet of said compressor to said heat exchanger, and means including a valve for selectively closing said second refrigerant line and opening said bypass line or closing said bypass line and opening said second refrigerant line, whereby said heat exchanger functions respectively as a heater or an air cooler, and means for conveying air to be conditioned over said evaporator and said heat exchanger.

References Cited in the file of this patent UNITED STATES PATENTS 

